Various advances in high power and high switching frequency electronic devices have been increasingly used in power applications in transportation systems, appliances, energy systems, and motor control. Such applications require power on the order of megawatts with operating temperatures on the order of 200° C. Exemplary high power devices are insulated gate bipolar transistors (IGBTs) that are semiconductor devices with four alternating layers and have a metal-oxide semiconductor gate structure. Due to the operating conditions of these devices, high dielectric breakdown voltage and high thermal conductivity are required in the device packaging. Typical substrates are ceramic-based direct bonded copper with flat copper. A bond line to such substrates is on the order of 0.4 mil to 3 mils.
Due to the high-power operation of these devices, it is important that the bond line be reliably uniform across the entire area of the bonded die. However, such reliably uniform bond lines have proven difficult to achieve with thin and/or uneven bondline thicknesses resulting in cracking as a result of high power switching that leads to thermal cycling, resulting in inelastic creep strain and crack growth. This results in partial or complete debonding of the die from the substrate.
Thus there is a need in the art for improved bonding systems that will maintain the required high dielectric breakdown voltage and high thermal conductivity necessary for high power and high frequency device applications.